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A single dose of the Pfizer / BioNTech vaccine offers 92.6% effectiveness in new calculations based on data sent to the US Food and Drug Administration (FDA), the researchers report.
Along with previous findings that a single dose of the Modern vaccine provides 92.1% effectiveness against SARS-CoV-2 infection, the researchers propose that it is time to postpone the second dose to extend protection to more people through single-dose mRNA vaccinations.
Danuta M. Skowronski, MD, of the British Columbia Disease Control Center in Vancouver, Canada, and Gaston De Serres, MD, PhD, of the National Health Institute of Quebec, Quebec City, Canada, wrote a letter published on 17 February in The new English medical journal.
Other experts disagree, however, saying that more data is needed before deviating from the two-dose regimen evaluated in clinical trials. They also point out that the FDA has granted emergency use authorization based on the two-dose studies.
Persisting in studies
Dr. Dial Hewlett Jr
“One of the things we should consider here is that when these vaccines are tested in clinical trials, they are tested in specific circumstances. In this case, two doses were used to achieve effectiveness. The studies didn’t really look at just one dose and trying to just go with it, “Dial Hewlett Jr, MD, medical director of the Westchester County Health Department’s Disease Control Division in White Plains, New York, said today during a news conference, sponsored by the Infectious Diseases Society of America .
Dr. Matthew Zahn
Matthew Zahn, MD, who also spoke during the IDSA briefing, agreed. “The CDC worked hard to place a premium on adhering to what is known science, and the tests looked at two separate doses of vaccine for less than 6 weeks.
“That’s really why we kept that recommendation. For my part, I think it makes a lot of sense,” said Zahn, medical director of the Division of Epidemiology and Evaluation at the Orange County Health Agency, Santa Ana, California.
In their correspondence, the authors report that they examined documents submitted to the FDA from 2 weeks after the first dose until the second immunization. They note that “even before the second dose …[the vaccine] it was highly effective. “
Do two doses extend protection?
Even if the effectiveness of a dose exceeds 90% at the beginning, how long this protection persists without a second dose remains an open question, said Hewlett, who is also a member of the Vaccines and Therapeutics Task Force of the National Medical Association COVID- 19.
“We don’t have any data studies saying that vaccines will be just as effective if you extend the time between the two doses,” said Zahn, who also serves as a liaison for the CDC’s Immunization Practices Advisory Committee.
Other researchers reported 94.8% efficacy against SARS-CoV-2 after two doses of the Pfizer / BioNTech vaccine in a previous study. The same report estimated a 52.4% single-dose effectiveness between the first and second doses, “but in their calculation, they included data that was collected during the first 2 weeks after the first dose, when immunity would still be increasing “, note Skowronski and De Serres.
“There may be uncertainty about the duration of protection with a single dose, but administering a second dose within 1 month after the first, as recommended, provides little additional benefit in the short term, while high-risk people who could have received a first dose with this vaccine supply is left completely unprotected “, they note.
“It may be true that, in the short term, one dose can be effective,” admitted Hewlett, “but we don’t know how long this protection will last, and will the second dose add up to that?” He explained that many public health officials want to simplify the administration of the vaccine, but “before we can support this, we are going to have to have data that looks at this.”
Skowronski and De Serres conclude their letter by stating that “given the current shortage of the vaccine, postponing the second dose is a national security issue that, if ignored, will certainly result in thousands of COVID-19-related hospitalizations and deaths this winter in the United States. United States – hospitalizations and deaths that would have been prevented with the first dose of the vaccine ”.
Skowronski has disclosed no relevant financial relationships. De Serres reported financial support from Pfizer for an unrelated study of seroprevalence of meningococcal antibodies.
N Eng J Med. Published online February 17, 2021. Correspondence
Damian McNamara it’s a staff Miami-based journalist. It covers a wide range of medical specialties, including infectious diseases, gastroenterology and intensive care. Follow Damian on Twitter: @MedReporter.
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